Official sources checked August 29, 2026

Williamson County, Texas septic permits and requirements

Texas permitting framework

Texas requires a permit and approved plan to construct, install, alter, extend, or repair an OSSF unless a specific exemption applies. TCEQ directs owners to the local permitting authority where an authorized local program exists and warns that local programs can be more stringent than statewide minimums.

Licensed OSSF professionals

TCEQ licenses or registers site evaluators, installers, maintenance providers, maintenance technicians, and designated representatives. County procedures can require particular licensed professionals based on system type, site conditions, and local rules.

County Engineer is the TCEQ-authorized OSSF authority

Williamson County states that its Engineer’s Office is authorized by TCEQ to administer the county OSSF program. The program processes applications and fees, performs permit and complaint inspections, investigates exposed-sewage complaints, and maintains permit records.

City of Austin is outside the county OSSF program

The county expressly excludes areas located within the City of Austin from its OSSF jurisdiction. Property owners should use the county address search or contact the OSSF office to confirm whether the county is the correct permitting authority before submitting an application.

Online applications only

Williamson County accepts OSSF applications through MyGovernmentOnline and states that paper and email applications are no longer accepted. A new system, repair, enlargement, or other modification requires an application through that process.

Development approvals can precede the septic application

For projects that change the property footprint, Williamson County requires a Certificate of Compliance before the OSSF application can be processed. If the proposed system is in a floodplain, a Floodplain Permit is required instead; a new driveway connecting to a county-maintained road can also require a separate driveway permit.

Inspections and records are part of the county program

The county performs OSSF inspections during permitting and complaint investigations and provides an open-records process for existing septic information. Record requests should include the property address and, when available, the subdivision, block, lot, or other legal-property information.

Official sources

• Texas Commission on Environmental Quality — Getting a Permit for an OSSF
• Texas Commission on Environmental Quality — OSSF Licensing
• Williamson County — On-Site Sewage Facilities
• Williamson County — Property Owner OSSF Application

SepticScope summarizes public-agency information for planning purposes. The permitting agency's current instructions control if they differ from this guide.